This invention relates to a stent delivery device used to ameliorate stenoses which form in bodily organs, such as blood vessels, bile ducts, trachea, esophagus, and urethra, especially to a stent delivery device which can implant an indwelling stent safely and easily in the intended stenosed part in blood vessels, particularly the blood vessels in the cardiovascular system in order to prevent restenosing of the treated area after the PTCA (Percutaneous Transluminal Coronary Angioplasty) treatment is performed.
The method which inserts a stent in stenosed parts of tubular organs and body cavities such as blood vessels, bile ducts, trachea, esophagus, and urethra, and thereby secures the passage space of the tubular organs and body cavities is conventionally used.
There are two types of stent used for this purpose, self-expandable stent and balloon-expandable stent, according to the function and indwelling method.
A balloon-expandable stent does not have the capability to expand by itself. This type of stent is set in an intended stenosed part by inserting a stent fitted over a balloon into the stenosed part and inflating the balloon to expand the stent (plastic deformation) and fix it in tight contact with the inside surface of that part.
A stent delivery device equipped with a balloon at the distal end is used to bring a balloon-expandable stent to an intended stenosed part, insert the stent into the stenosed part, and expand the stent in the stenosed part.
There are some conventional stent delivery devices which are provided with a stopper for preventing the stent from coming off, on the distal side of the stent expanding balloon. However, measures to prevent the stent from sliding out of place toward the proximal end are not adequate. Further, the balloons of conventional stent delivery devices have tapered portions on the distal and proximal sides of the inflatable portion which inflates into the shape of an approximately uniform-diameter cylinder. Therefore, if the stent shifts out of place on the balloon, one end portion of the stent is located over a tapered portion of the balloon. Since the tapered portions of the balloon inflate into the shape of a cone, the end portion of the stent is not fully expanded, causing an insufficient amelioration of the stenosed part.
Therefore, the object of this invention is to provide an improved stent delivery device wherein the stent fitted over the balloon rarely shifts out of position, or if the stent happens to shift a little of position, the entire stent still can be expanded completely into the desired shape.